Tone-generating device for electronic musical instrument

ABSTRACT

An electronic musical instrument comprises a keyboard associated with a DC power source to produce a controlling DC voltage, a plurality of variable frequency oscillators which produce tone signals of frequencies determined by the controlling DC voltage and which include a control rate adjuster so that the oscillators are always in harmonic relations very approximately, switching circuits for switching said tone signals, and means to convert the tone signals into sounds.

United States Patent Shigeru Yamada [72] Inventor 39-14, Nakazawa-cho, Hamarnatsu-shi, Shizuoka-ken, Japan [2]] App]. No. 20,165 [22] Filed Mar. 17, 1970 [45] Patented Nov. 30, I971 [54] TONE-GENERATING DEVICE FOR ELECTRONIC MUSICAL INSTRUMENT 2 Claims, 3 Drawing Figs.

[52] US. Cl 84/1J9, 84/122, 84/123 [51] Int. Cl G10h 1/06 [50] Field of Search 84/l.0l, 1.1 1, 1.19, 1.22, l.03, 1.24, DIG. 4, l.23,DlG. 7, DIG. 8

[56] References Cited UNITED STATES PATENTS 3,236,931 2/1966 Freeman 84/123 2,697,959 12/1954 Kent 84/122 3,038,364 6/1962 Bergman 84/1 .24 3,429,978 2/1969 Freeman 84/124 OTHER REFERENCES T. S. Fox, A Waveform Synthesizer for Technical Training," Electronic Engineering, Sept. 1955, pp. 374- 378.

Primary Examiner-D. F. Duggan Assistant Examiner-Stanley J. Witkowski A!t0rneyHO1man & Stern ABSTRACT: An electronic musical instrument comprises a keyboard associated with a DC power source to produce a controlling DC voltage, a plurality of variable frequency oscillators which produce tone signals of frequencies determined by the controlling DC voltage and which include a control rate adjuster so that the oscillators are always in harmonic relations very approximately, switching circuits for switching said tone signals, and means to convert the tone signals into sounds.

VARIABLE-FREQUENCY 3 CONTROL OSCILLATORS l KEY BOARD TERMINAL 9 JSWITCHING CIRCUITS I I2 TONE-COLOR CIRCUIT 5 |o E I I 6? H l |4 LOUD SPEAKER E s 7 i I3 AMPLIFIER L J CONTROL RATE ADJUSTERS 2 CONTROL-VOLTAGE GENERATOR PATENIED NUV30 |97l KEY 3,624,265 SHEEI10F2 FlG.l

VARIABLE FREQUENCY 3 CONTROL OSCILLATORS BOARD TERMINAL 9 SWITCHING CIRCuITs X 4 I2 TONE-COLOR CIRCUIT E L I4 LOUD SPEAKER 8 I I3 AMPLIFIER CONTROL RATE ADJUSTERS 2 CONTROLvOLTACE GENERATOR INVENTUR Skit-mu Yam MI ATTORNEY;

PATENTEUNnvsdrsn SHEET 2 [IF 2 INVENTOR 8H G-Eku Vnmnon TONE-GENERATING DEVICE FOR ELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION This invention relates generally to electronic musical instruments, and more particularly to a device for generating musical tones in very approximate but not just exact harmonic relations for giving richness to musical sounds.

In order to obtain richness and wide variety in musical sounds, various types of tone-generating devices are heretofore known. A typical one of them is a :so-called coupler means wherein an output frequency from a certain oscillator is admixed with higher harmonics obtained from separate oscillators, the oscillating frequency in each of the oscillators being a multiple or a submultiple of the one frequency by a number as, for instance, an even integer. As a variable frequency tone generator, there is known a variable frequency oscillator, the frequency of which is determined and controlled by a DC voltage which is applied to the control terminal and is varied by depressing a different key on the keyboard.

The inventor conducted thorough study about musical sounds and has drawn a conclusion that when a musical sound having naturalness is desired, each of the harmonic frequency components is preferably deviated a little from the exactly correct harmonic integer relationship. This deviation is more important when it is desired to obtain a broad and rich sensation of sounds such as those rendered from a pipe organ or in an orchestra where various musical instruments are played in ensemble.

For realization of the above-described frequency deviations of the harmonic components from the correct integer multiple relationship to the fundamental frequency, a plurality of separate variable frequency oscillators may also be employed, and the frequencies of the oscillators may be controlled simultaneously employing a single control voltage.

However, when these frequencies are controlled through a wide range by a single control voltage, sounds inducingunnatural and dissonant sensation have been frequently ob tained, since the control rates (mathematically, d(frequency/ )/a'( control voltage) which mean the variation characteristics of frequencies in these oscillators in response to the single control voltage are, in an ordinary case, not equal to each other, and the harmonic relationship in these frequencies obtained from the respective oscillators becomes far from the integer relationship. Such a drawback is further aggravated by the fact that the variation rates of the oscillation frequencies of the variable frequency oscillators depending on the variation of the control voltage may be different widely by the lack of uniformity of the parts employed in these oscillators. For instance, the variation rate of the oscillating frequency in an astable multivibrator or in an astable blocking oscillator depending on the control voltage may be widely changed by the allowance variation of the base-emitter voltage V,,,,- of the transistor included therein.

To eliminate the above described disadvantages, the component parts must be selected carefully, or a plurality of control voltages individually adapted to the corresponding oscillators must be employed. However, such procedures are excessively troublesome and uneconomical.

SUMMARY OF THE INVENTION Therefore, the principal object of the present invention is to provide a novel device for generating musical tones for an electronic musical instrument, whereby the above described drawbacks of the conventional tone generators are substantially overcome.

Another object of the present invention is to provide a novel organization of the tone-generating device wherein a plurality of oscillators are controlled from a single control voltage applied thereto.

Still another object of the present invention is to provide a novel sound-generating device for an electronic musical instrument wherein the harmonic frequencies obtained from the plurality of oscillators are slightly deviated from the exact harmonic relationship, whereby musical tones resembling those of a natural musical instrument can be obtained.

These and other objects of the present invention can be achieved by a device for generating sounds to be employed in an electronic musical instrument having keys, which device comprises a control voltage generator associated with the keys and generating when a key is depressed, a DC control voltage representing a tone name of the key being depressed; a plurality of variable frequency oscillators connected to the control voltage generator, each oscillating a tone signal having a frequency determined by the control voltage and substantially harmonically related to each other upon receipt thereof, and each except one including a control rate adjuster for varying the changing rate of the oscillation frequency in response to the change of the control voltage; switching circuits connected to the oscillators and associated with the keys for receiving and keying output signals from the oscillators upon depression of the key; a tone color circuit connected to the switching circuits for receiving the tone coloring output signals from the switching circuits; and an amplifier and a loudspeaker for converting output signals from the tone color circuit into sounds.

The nature, principle, and utility of the invention will be more clearly apparent from the following description with respect to a preferred embodiment thereof, when read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing,

FIG. 1 is a block diagram showing a tone-generating device constituting one embodiment of the present invention,

FIG. 2 is an actual circuit diagram showing the construction of a preferred embodiment of a DC voltage-controlled variable frequency oscillator to be used in this device, and

FIG. 3 is a circuit diagram showing the whole construction ofone embodiment of this invention.

DETAILED DESCRIPTION Referring now to FIG. 1 in the accompanying drawings, it is seen that a tone generating device according to the present invention comprises a keyboard 1, a control voltage generator 2 including a DC power source and a voltage divider, a control terminal 3, three variable frequency oscillators 4, 5, and 6 for generating signals having frequencies determined by the control voltage, control rate adjusters 7 and 8 for controlling relations between the oscillation frequencies and the control voltage of the variable frequency oscillators 4, 5, and 6, switching circuits 9, l0, and 11 which open or close the output signals from the variable-frequency oscillators under the operation of the keyboard 1, a tone color circuit 12 which mixes the output signals from the switching circuits 9, l0, and I1 and filters so that a desired tone color is obtained, an amplifier 13, and a loudspeaker 14.

With this construction of the tone generating device, when a certain key in the keyboard 1 is depressed, a control-voltage from the control voltage generator 2 having a valve representing a tone name of the depressed key is applied to the control terminal 3, whereby the variable frequency oscillators 4, 5 and 6 are oscillated respectively at the frequencies determined by the control voltage. The output signals from the variable frequency oscillators 4, 5 and 6 are thereafter sent to the switching circuits 9, l0, and 11. Since the switching circuits 9, l0, and II are conducting at the time the corresponding key is operated, the output signals are then sent to the tone color by mixing the output signals from the variable frequency oscillators and passing the thus mixed output signals through a filter included in the tone color circuit 12.

Now suppose the oscillating frequencies of the variable frequency oscillators 4, 5, and 6 having an integer relationship (of, for instance, 1 10, 220, and 330 Hz. respectively). Since each of the variable-frequency oscillators is oscillating independently at the above-mentioned frequency (each of the frequencies is not maintained exactly in the above-described integer relationship as in the case wherein these frequencies are obtained from a frequency division system), the tone sensation of the resultant sound produced by mixing the output signals from the variable frequency oscillators includes harmonic components having slightly deviated frequency relationship from that of the abovedescription, whereby a kind of beat sounds are heard in the output obtained from the tone color circuit 12, and the above described rich and broad tone sensation is thereby obtained.

The control rate of the variable frequency oscillators 5 and 6 with respect to the frequency control voltage can be adjusted by the control rate adjusters 7 and 8, so that the oscillation frequencies of the oscillators 5 and 6 are changed by a substantially same rate as the frequency change of the oscillator 4 when the control voltage is changed through a wide range, whereby the harmonic relationship (not of a exact integer, but of a very approximate integer) of the three frequencies is maintained to be substantially constant throughout the scale compass of the electronic musical instrument. A typical example of the voltage-controlled variable frequency oscillator provided with the control rate adjuster is shown in detailed in FIG. 2.

In FIG. 2, the oscillator is constructed by an astable (freerunning) multivibrator including transistors Q, and 0,, resistors R R R and R,,, and capacitors C, and C The power for operation is supplied from a DC power source E through resistors R and R and diodes D and D,, a capacitor C being a bypass for AC signal. The control DC voltage for determining the oscillation frequency is supplied from a DC power source E, through resistors R and R diodes D, and D and a switch SW to a control terminal 3 of the multivibrator. The resistor R together with the switch SW, and the resistor R function to change the oscillation frequency of the oscillator. When the switch SW is in contact with the higher tap position of the resistor R and thereby the higher control voltage is applied to the terminal 3, the oscillation frequency becomes higher. When the sliding contact of the variable resistor R, is set nearer to the positive side of the power source E the oscillation frequency becomes lower. The variable resistor R, functions to change the control rate of the oscillation frequency in response to the change of the voltage of the terminal 3. When the resistor R, is set at the higher value, the oscillation frequency is varied more widely to the same change of the control voltage by the switch SW. In designing the circuit, the tap positions of the resistor R, are determined to oscillate the respective tone pitch signals in the chromatic musical scale, using a standard circuit model with the resistors R and R, set at proper standard values. In manufacturing the device at a factory in a mass-production quantity, the resistors R are prepared having taps at such positions determined by the designing, and then the switch is brought into contact with the taps one by one to see whether the frequency intervals are too wide for the chromatic scale or too narrow. If too narrow, the resistor R, is varied to have a higher value until the intervals become correct for the chromatic scale. This variable resistor R, constitutes the control rate adjusters having the important function in this invention. And next, the absolute value of the oscillation frequency is examined. If it is too higher eg 240 Hz. for the note A =220 Hz. the sliding contact of the variable resistor R is brought more positive to lower down the frequency. The adjustment by the resistor R, and the resistor R is carried out a few times alternately, and then the switch SW can selectively determine the oscillation frequency at the respective pitches of the notes in the chromatic musical scale. The variations of the resistor R, also affects the absolute frequency and the variation of the resistor R also affects the control rate, but the repeated adjustment as mentioned above finally brings the device into a correct or substantially correct condition. In an actual instrument, the switch SW constitutes key switches in a playing keyboard. The player has only to manipulate the laying keys during music performance. The resistors R, an R have no longer to be ad usted after the device comes out of the factory, except when the device is subjected to reparation such as replacement of the transistor. The diodes D,, D D and D is for the temperature compensation together with the resistors R and R,

FIG. 3 shows one embodiment of the invention having the basic construction of FIG. I, with the detailed circuit dia grams, employing the variable frequency oscillators shown in FIG. 2 and other circuits of conventional constructions, so that the realizability and the operation of this invention can be better understood. In this figure, a capacitor C, is provided to obtain a sustain effect. This capacitor C, keeps the control voltage for a while even after the keyboard I is released, which permits the oscillators 4, 5, and 6 to maintain their oscillations of the same frequencies, and the sustain effect in the output sounds can be obtained through an operation of the switching circuits 9, 10, and 11.

As is apparent from the above description, the fundamental and the harmonic frequencies are not maintained in an exact integer relationship, whereby an advantageous effect simulating natural auditory sensation of the sounds is imparted to the output sounds. Furthermore, since the plurality of variable frequency oscillators is controlled by a single control voltage, a coupler system of a simple and economical construction can be obtained. When this device is assembled into an electronic musical instrument, output sounds of excellent quality similar to natural sounds can be obtained when pedals or a solo device of the musical instrument is operated.

Iclaim:

l. A device for generating a plurality of harmonically related sounds in an electronic musical instrument having keys; which device comprises a control voltage generator associated with said keys and generating, when a key is depressed, a DC control voltage representing a tone name of said key being depressed; a plurality of variable frequency oscillators connected to said control voltage generator, each oscillating a tone signal having a frequency determined by said control voltage and substantially harmonically related to each other upon receipt thereof, and each except one including a control rate adjuster for varying the changing rate of the oscillation frequency in response to the change of said control voltage; switching circuits connected to said oscillators and associated with the keys for receiving and keying output signals from said oscillators upon depression of said key; a tone color circuit connected to said switching circuits for receiving the tone coloring output signals from said switching circuits; and an amplifier and a loudspeaker for converting output signals from said tone color circuit into sounds.

2. A device as defined in claim 1, wherein said control voltage generator includes means providing a tone sustain effect, said means comprising a storage capacitor coupled across said voltage generator for maintaining said DC control voltage for a period of time after release of said keys.

II l' l I 

1. A device for generating a plurality of harmonically related sounds in an electronic musical instrument having keys; which device comprises a control voltage generator associated with said keys and generating, when a key is depressed, a DC control voltage representing a tone name of said key being depresseD; a plurality of variable frequency oscillators connected to said control voltage generator, each oscillating a tone signal having a frequency determined by said control voltage and substantially harmonically related to each other upon receipt thereof, and each except one including a control rate adjuster for varying the changing rate of the oscillation frequency in response to the change of said control voltage; switching circuits connected to said oscillators and associated with the keys for receiving and keying output signals from said oscillators upon depression of said key; a tone color circuit connected to said switching circuits for receiving the tone coloring output signals from said switching circuits; and an amplifier and a loudspeaker for converting output signals from said tone color circuit into sounds.
 2. A device as defined in claim 1, wherein said control voltage generator includes means providing a tone sustain effect, said means comprising a storage capacitor coupled across said voltage generator for maintaining said DC control voltage for a period of time after release of said keys. 